Mesoporous Pd/Co ₃ O ₄ nanosheets nanoarrays as an efficient binder/carbon free cathode for rechargeable Li-O ₂ batteries

In this work, two shapes of mesoporous Co ₃ O ₄ nanoarrays (i.e., nanosheets, nanowires) were synthesized through a facile hydrothermal method on nickel foam (Ni foam) substrates and tested as the Li-O ₂ cathodes. The comparison of these two shapes of Co ₃ O ₄ nanoarrays revealed that the single crystalline feature of Co ₃ O ₄ nanosheets with a predominant high reactivity {112} exposed crystal plane, favorable nanostructure and high specific area displayed better catalytic performance. Furthermore, a new binder/carbon-free Pd nanoparticles (PdNPs) decorated Co ₃ O ₄ nanosheets cathode was also fabricated through the chemical reduction method. The presence of PdNPs effectively promotes the uniform growth of a fluffy, porous discharge product Li ₂ O ₂ layer on the surface of Pd/Co ₃ O ₄ electrode. The Pd/Co ₃ O ₄ electrode catalyzed Li-O ₂ battery exhibited a higher specific capacity (1551 mAh g ⁻¹ at 50 mA g ⁻¹ ), lower over-potential and longer cycle life over 72 cycles at 100 mA g ⁻¹ with the capacity limited at 300 mAh g ⁻¹ . The superior catalytic performance for Li-O ₂ batteries is ascribed to the unique design in both component and architecture of Pd/Co ₃ O ₄ electrode.